April 25, 2014
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Breast Cancer

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Cancer cells vs. normal cells: what's different?

To understand what cancer is, it is important to first understand how the body's cells normally work.

How does the body grow and maintain itself?

The body is made up of tiny cells - for example, skin cells, muscle cells, heart cells, nerve cells, and bone cells. When a baby grows, the number of cells increases very quickly. A cell becomes a bit larger, then divides into 2 "daughter" cells (Figure 1). After a period of time, each of these cells divides, and so on.

A cell grows a bit larger then divides into two cells

Figure 1

Normal cell division. A cell grows a bit larger then divides into 2 cells.

Once a child grows to adulthood, the size of the body no longer increases. However, our bodies go through a lot of wear and tear, both inside and outside. Worn-out cells constantly need to be replaced, so cell division still takes place, but more slowly. An obvious "outside" change is the tiny bits of dead skin flaking off as the skin constantly renews itself.

Although our bodies' cells continue to divide to replace worn-out cells, this happens in a very ordered, systematic way. The reason is that each cell carries genetic instructions that regulate how fast the cell should grow and divide and when the cell should die. A balance between cells growing and dying keeps our bodies functioning normally.

When cell growth goes out of control

Cell growths can be classified as either benign or malignant.

Benign growths

Sometimes a cell starts to grow without regard for the normal balance between cell growth and death, and a small, harmless (or benign), lump of cells will form. A benign growth can occur in any part of the body, including the prostate, skin, or intestine.

Malignant growths

In other cases, a cell may grow and divide with complete disregard for the needs and limitations of the body. Cells that have this aggressive behaviour are called malignant. They have the potential to grow into large masses or spread to other areas of the body. More commonly, a mass of such cells is called a cancer. When clumps of these cells spread to other parts of the body, they are metastases. A cancer that continues to grow can eventually overwhelm and destroy the part of the body or particular organ where it is located.

There are many different types of cancer

Each type of cancer is distinguished by the cells in which it originates. For example, a cancer may arise from cells of a gland, muscle cells, nerve cells, or fat cells. Each of these cancers behaves differently and has a different name:

  • adenocarcinoma (cancer of a gland)
  • leiomyosarcoma( cancer of the muscle cells)
  • neurosarcoma (cancer of the nerve cells)
  • liposarcoma (cancer of the fat cells)

Cancer cells have the ability to spread

Most normal cells remain in the area where they belong and do not spread to other parts of the body. Cancer cells disregard this principle and may spread through the body (metastasize) in several ways. These include direct invasion and destruction of the organ of origin, or spread through the lymphatic system or bloodstream to distant organs such as the bone, lung, and liver.

When a cancer spreads, it retains the properties of the original cancer. For example, prostate or breast cancer that spreads to the bones is still a prostate or breast cancer. Under the microscope it looks different from a cancer that started in the bones, and it responds to treatment like a prostate or breast cancer, not a bone cancer.

The original cancer is called the primary cancer. A cancer that has spread to another site is called a secondary or metastatic cancer.

Cancer cells can trick the immune system

The immune system consists of a group of cells called white blood cells that are specialized to recognize and destroy "foreign" material in the body such as bacteria, viruses, and unfamiliar or abnormal cells. Cancer cells somehow manage to slip through this detection system without triggering the immune system to start fighting, either at the primary cancer site, in the blood vessels, or at the site of the distant spread.

 
Excerpt from the Intelligent Patient Guide to Prostate Cancer by S. Larry Goldenberg, MD 
in association with the MediResource Clinical Team 

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